The purpose of this proposal is to investigate the development of saccadic, pursuit, and vergence eye movement control in 6-, 12-, and 18-week-old human infants. The overall goal is not only to characterize significant developments in oculomotor control that occur during the first four postnatal months, but also to assess a variety of sensory abilities that may limit the effectiveness with which each eye movement system is guided. Studies of the saccadic system will use an automated eye monitoring system to examine the smallest target displacement that reliably elicits a saccade and the forced-choice preferential looking (FPL) procedure to examine sensory estimates of the threshold for target displacement. Studies of the pursuit system will use FPL to examine thresholds for motion detection, velocity discrimination, and the motion after effect and the eye monitoring system to examine predictive tracking in young infants. Studies of the vergence system will use the binocular capabilities of the eye monitoring system to examine fusional vergence, lateral phorias, the AC/A ratio, and the resting position of vergence; binocular pupillometry and the visual evoked potential (VEP) to examine monocular suppression; and an automated refraction device to examine the resting position and accuracy of accommodation. These experiments will aid in determining if the inefficient and inaccurate oculomotor control exhibited by young infants is the result of degraded sensory information or a deficit in motor or sensory-motor programming. Finally, the sensory and oculomotor assessment techniques developed for use with normal infants will be applied to a small sample of clinical patients with ocular anomalies.